I’ve got through 4 sets of pads recently, the last set lasted a few weeks before the horrible squeal is happening again.

I used Muc off nano on drivechain but try and avoid brakes, and use fenwicks brake cleaner.

I do mask the brakes off when cleaning and was particularly careful last time, no spray lubes and wet lube on chain whilst brakes masked/excess dried off etc.

Interestingly this time I’d been away for a week, they were fine before I went and dodgy when I got back. I read something about possible pistons leaking (Shimano M506) but the LBS dismissed this.

What else can I do at this point? Could the rotors be contaminated to the point where a clean in a bucket+fenwicks isn’t making a difference and just replace them, or could the brakes be leaking (can’t see anything obvious)
¯\_(ツ)_/¯

shimano brakes are notorious for tiny leaks that cause this. Put some tissue paper between the pads and pistons and clamp the brake on overnight – that will tell you. Search on here for plenty of threads on this and IIRC shimano were doing warranty returns for this issue

How old are the brakes? Ive had the same thing happen to Shimano brakes after a few years of use, a fine mist of brake fluid on the pads due to the seals perishing.

Have you a blowlamp ?.

Many(inc) use heat to burn off the contaminate. Not to red hot, but apply the lamp until it smokes, take the heat off, then on again and thus until the pad stops smoking. Then a piece of 1000 grit wet and dry on a flat surface to dress off the face.

* Awaits derision.

I keep this thread bookmarked, have fixed the issue with older Shimano calipers by replacing the o ring as per the thread.

Leaking Shimano Calipers – possible solution

Tbh I don’t understand why you’re going so crazy cleaning discs / brakes – as long as the brakes don’t need bleeding and the pads are in ok shape I just don’t touch them.

I’d just try not going near them with any kind of cleaning product and see if that helps.

If it doesn’t he’ll it’s very likely you have a micro leak from the Shimano caliper – so many people seem to get this problem it’s untrue. I had some shimano deores that did this pretty soon after I put them (brand new) onto the bike. I just got rid and no further shimano brakes will find their way onto any of my mtb’s.

Generally you just need to buy a new brake in this latter situation.

Cheers all

Yeah had the front replaced already (unrelated issue) and this is the original rear from a 17 bike so I guess out of any recall period or whatever.

Will check out the o-ring thread

Are they losing power as well? If they were badly contaminated I’d expect them not to work that well. Have you tried copper grease on back and side of pads? Often stops squealing, also check alignment of brakes